Grass and weed cutting trimmers of the line cutting type have become very popular. Their cutting technique is to flail the end of a line rapidly around an axis of rotation, and the flailing line cuts the grass or weeds. The line cutting trimmer is inherently safer than the blade type, and this accounts for much of its popularity. Blade type cutters utilize rigid blades, which if they strike the operator, can cause serious injury and even amputation of small extremities such as fingers and hands. The flailing line causes much less damage, but still it is not desirable for the operator to be struck by the flailing line, so a guard is provided.
However, in order for the trimmer to do its work, the line must project beyond the limits of the guard at some point, or the guard would protect the grass and weeds from the line. Line cutting trimmers need one function which a blade cutter does not--replenishment of the line which abrades away or breaks away in use. In the blade-type cutter, the blades are simply sharpened or replaced. The line, however, is usually made of flexible plastic or of braided wire sheathed in flexible plastic. After a period of usage an end segment of the line will have become abraded away or broken away, and it must be replaced. A conventional technique is to feed new line incrementally from a spool in the rotating head of the cutter. One such mechanism is known as the "Bump Head". When replenishment is desired, the head is bumped sharply on the ground, and an incremental length of line is issued to replace the lost segment.
A problem inherent in this technique is the uncertainty of the free length of the line. It is best and most efficient practice for this length to be appropriate to the size of the trimmer and to the speed and power of its drive. In other words, there is a best length for the line. It is known to place a very sharp blade inside the guard in the path of the flailing line to cut the line to a specific length. This does the job of cutting the line very accurately and expeditiously, but the cut-off segments are in rapid and uncontrolled motion, and can constitute a projectile which involves potential risk to the operator and the by-standers.
It is an object of this invention to provide the advantages of a line-cutting type trimmer, but without forming flying projectiles of cut-off line segments.